Since Republicans took back the U.S. House in the 2010 elections, abortion has been a fairly constant theme. The House took eight separate abortion-related votes in 2011 — the most in a decade, according to NARAL Pro-Choice America.

But now abortion-rights advocates may have found something they like that may even get through Congress and to President Obama's desk.

Last month, with little notice or fanfare, Sen. Jeanne Shaheen, a New Hampshire Democrat, got an amendment included in the huge annual Department of Defense bill that would permit military health insurance to cover abortions for servicewomen whose pregnancies are the result of rape or incest.

Three Republican senators — John McCain of Arizona, Scott Brown from Massachusetts and Susan Collins of Maine — voted for the amendment.

Shaheen, who is now fighting to keep the language in the bill, says it's a matter of simple equity.

"Federal civilian employees, Medicaid recipients, even federal prison inmates are guaranteed affordable access to abortion in cases of rape," she said at a news conference. "But women in uniform are on their own."

Shaheen is calling out the big guns, so to speak. At the news conference Thursday she was flanked by two retired military officers who are helping lobby to prevent the language from being removed from the bill.

"Women compose almost fifteen percent of our military, serving with courage and distinction in every branch of service," said retired Major General Dennis Laich. "Lifting this ban is not only a matter of basic fairness; it is also a matter of ensuring military readiness."

Major General Gale Pollock, former surgeon general for the army, agreed. "When a servicewoman is raped, becomes pregnant, and chooses to end a pregnancy caused by an act of violence, she should not have to scramble to find the funds she needs to pay for an abortion," she said.

But what may end up keeping the amendment is less the lobbying of retired Army brass, and more simple math.

Because the amendment is currently in the bill, it will require 60 votes in the Senate to take it out. That's something opponents have conceded will be difficult, if not impossible.

A majority of House members oppose abortion rights, and it's all but certain the version of the bill in that chamber won't include similar language. So the question will have to be settled when the House and Senate meet to hammer out a compromise. If the abortion language survives, even if a majority of the House disapproves, its only option will be to vote down the entire defense bill. That is traditionally a highly unlikely event.

Meanwhile, anti-abortion groups have been mostly silent on the issue. While it was being debated in the Senate they were busier pushing a bill in the House to ban abortion on the basis of sex-selection. That measure failed to pass.